The present invention is directed toward the achievement of desirable values of wheel slip for vehicles of any wheelbase under widely varying conditions of vehicle load weight and distribution of such weight, and varying tire-road interface conditions. Various prior art patents disclose skid control systems having similar goals. For example, U.S. Pat. No. 3,566,610 issued on Jan. 19, 1971 to Teldix Gmbh upon an application filed in the name of Heinz Leiber generally discloses brake control systems for preventing wheel locking. However, the electronic embodiments disclosed in this patent are capable of reducing brake line pressure only in response to a fixed incremental decrease in wheel speed. Also, see cross-referenced U.S. Pat. No. 3,827,760 issued on Aug. 6, 1974 to Wagner Electric Corporation upon an application filed in the name of the present applicant, which discloses a wheel slip control system operative to reduce braking force at least in response to a change in wheel speed exceeding a variable reference increment of wheel speed, said change being from the value of wheel speed at the time the rate of change of wheel speed exceeds a predetermined threshold. In this system, a significant level of system adaptivity is achieved by the use of a variable reference increment of wheel speed, which is directly related to the rate of change of wheel speed.